/*元素选择器*/
h1{
    color:red;
}
/*id选择器*/
#container{
    color: blue;
}
/*类选择器*/
.center{
    color:green;
}
/*属性选择器*/
p[data-bind ]{
    color: yellow;
}

span+，change{
    color: firebrick;
}
span~.change2 {
    color: blueviolet;
}
span{
    background: #fff;
}
P>span{
    background: chocolate;
}
div span{
    background: red;
}
/*未访问链接*/
a:link{
    color: blue;
}
a{
    text-decoration: brown ;
}
/*已访问链接*/
a:visited {
    color: mediumpurple;
}
/*鼠标悬停*/
a:hover {
    font-weight:bold;
    background: yellow ;
    text-decoration: brown ;
}
a:active {
    /*激活链接*/
}